The safety of players is at the top of the agenda after Jack Grealish was attacked on the pitch and Chris Smalling was confronted, with the Professional Footballers' Association calling for a full inquiry after a dark day for the sport.
Two fans were arrested following separate incidents on Sunday, with Aston Villa skipper Grealish punched by a fan just hours before a spectator ran towards Smalling and appeared to push him during Manchester United's 2-0 defeat at Arsenal.
Grealish was struck on the side of the head after nine minutes as he stood in Birmingham's penalty area during the derby match at St Andrew's.
Grealish went on to hail it the 'best day of his life', as he recovered from the incident to score the winner. The fan, named by West Midlands Police as 27-year-old Paul Mitchell, was later charged with invading the pitch and assault.
Birmingham confirmed Mitchell would be banned for life from St Andrew's.
Arsenal later pledged the same punishment would be imposed on pitch invader at their match. Sunday's incidents came after Rangers captain James Tavernier found himself face to face with a fan on Friday night who had jumped out of the Hibernian support before being led away.
In a statement released before the Smalling incident the PFA said: "The PFA condemns in the strongest possible terms the actions of the individual who has encroached on the field of play and attacked Aston Villa midfielder Jack Grealish.
"There needs to be a full inquiry into the incident to ascertain why in a fixture with such a charged history, a fan was able to run onto the pitch virtually unchallenged and assault a player.
"The PFA is concerned that we've seen elements of this type of behaviour coming back into the game, with several high-profile crowd related issues this season.
"Over the last few decades there has been a great improvement in matchday security, however incidents like this demonstrate certain problems have not been eradicated and that players can be particularly vulnerable.
The cream always rises... ⚽️ #AVFC pic.twitter.com/4C0TOSSjZw — Jack Grealish (@JackGrealish1) March 10, 2019
"We must address issues of violence and player safety – this should include continued efforts with regards to education but be underpinned by strong punishments and sanctions."
Grealish scored a 67th-minute winner and later told Sky Sports Football: "(This is the) best day of my life. To come here, captain Aston Villa and score the winner is what dreams are made of, especially for me as a Villa fan."
Birmingham issued a statement apologising to Grealish while Villa also released their own statement saying: "A red line has been crossed by this cowardly on-field assault on a player, which is unprecedented in English football."
West Midlands Police also confirmed a steward was "spoken to" in the aftermath of the Villa goal after television footage appeared to show him pushing Grealish as the player celebrated but no offence had been reported.
After Smalling was confronted at the Emirates, Arsenal released a statement saying: "We utterly condemn the behaviour of the individual who ran onto the pitch and approached Chris Smalling during today's match. We would like to apologise to Chris and Manchester United, and are pleased that the individual was apprehended and arrested."
The EFL and Football Association condemned the incidents, while the Premier League was contacted for comment.
